Coastal zone of the Wadden Sea: sedimentation and erosion

The intertidal coastal zone of the Wadden Sea consists of saltmarshes and adjacent mudflats. The zone is important because of its natural values ​​and because it protects the land against flooding. However, it is threatened by accelerating sea level rise. Knowledge about sedimentation, erosion and the interaction with vegetation is central to gain a better understanding of the growth capacity of the saltmarshes and mudflats.

RPAS based mapping combined with Structure-from-Motion photogrammetry offers possibilities to develop accurate, high-resolution maps and 3D models. During 2019/2020, we collaborated with the University of Twente, Blik van Boven and ATMOS UAV and carried out a pilot project to gain experience mapping intertidal coastal zones. We used the Atmos Marlyn to map more than 300-400 ha in 2-3 hours. Mapping was done before and after winter which allows to assess changes in elevation.

Marlyn on the saltmarshes.
  Aerial images show detailed structures on the marshes and mudflats.

We constructed maps and 3D models and visualized sedimentation and erosion that took place during the winter storms. Thanks to the high accuracy GNSS-PPK technology on the Marlyn, we were able to detect changes that were in the order of cm. Preliminary analyses show erosion on the outer mudflats and sedimentation on the mudflats within the brushwood groin fields. This information helps us to better understand the response and adaptive capacity of these intertidal systems to sea level rise and changing climate and helps to develop nature-based coastal protection solutions.

Sedimentation and erosion on the intertidal flats and in the brushwood groin fields between autumn 2019 and spring 2020. The graphs on the right represent the change in elevation along transects

Thanks to a NWO-ORC grant awarded to Dr. Bas Borsje from the University of Twente we continue this research over the next years. Furthermore, within the context of the research program led by Bas, these empirical results will be combined with hydrodynamic models to gain insight into the factors that drive the development of the coastal zone and the role it plays in protecting the land.